Generating electrical power from mechanical energy is a type of alternate energy that is commonly found in locations where electrical energy can be generated from currents of flowing fluids, such as water or air. Examples include the generation of electricity by hydro-electric dams and wind turbines.
Typically, a system for generating electricity from flowing fluids has a turbine that is operatively connected to a generator by a rotatable shaft or flexible cable. The turbine is often placed within the current of the flowing fluid, such as water or wind and as the current flows or passes by the turbine, the turbine is caused to rotate. The rotational movement of the turbine is mechanically transferred to the generator through the rotatable shaft or flexible cable where the mechanical energy can be converted into electrical energy.
Electrical energy generated can then be transferred to a commercial power grid, can be transferred directly to electrically powered equipment or can be stored in batteries for future use.
It is known to have multiple turbines operatively connected to a single generator or have multiple turbines each operatively connected to its own generator for generating electrical power.
Hydro-electric generators typically have a submerged or semi-submerged turbine, such as a propeller, that is placed within a flowing body of water and are usually oriented to be directly in line with the direction of flow of the water or current. That is, a rotational axis of the turbine is substantially parallel and in-line with the direction of flow of the current.
Rotors having helical surfaces are known for generating power from the flow of water. U.S. Pat. No. 1,371,836 to Antz discloses a rotor positioned within a stream to assume an oblique position with relation to the direction of flow. The rotor has a plurality of vanes or blades spaced apart from one another along a shaft, providing a plurality of passages between each of them for permitting water to flow around the rotatable shaft. International Published Patent Application WO 2004/067957 A1 to Eielsen (Eielsen '957) discloses a screw turbine device having a single start helical blade rotatable about a central axis. Eielsen '957 teaches that an angle between the direction of the flow of the current relative to the central axis (or axis of rotation of the turbine) must be approximately equal to that of the pitch angle, being the angle of the outer edge of the helical blade relative to the central axis.
International Published Patent Application WO 2006/059094 A1 to Bowie discloses an apparatus for generating power from a flowing fluid, such as from water or wind. Bowie's apparatus has one or more helical blade sections held in position within a current by cables or other anchoring means and oriented such that an angle between the axis of rotation of the helical blade and the direction of the flow of the fluid is preferably kept less than 30 degrees. International Published Patent Application WO 2009/093909 A1 to Eielsen (Eielsen '909) teaches the turbine screw device of Eielsen '957, except for having two helical screws adjacent one another for improved utilization of the flowing water.
Similarly, windmills typically have a turbine which rotates about a longitudinal axis (or axis of rotation) in response to a wind blowing or passing thereby. The rotational movement of the turbine is mechanically transferred to a generator by a rotatable shaft for producing electrical energy. Certain prior art windmills have a nacelle housing a rotor, rotatable shaft, and generator therein. Other prior art windmills have an extended rotatable shaft that operatively connects the turbine with a generator that is spaced away therefrom.
Typically, windmills are classified according to the orientation of turbine's axis of rotation. A windmill having a horizontal axis of rotation is more commonly known as a HAWT (horizontal axis wind turbine) while a windmill having a vertical axis of rotation is known as VAWT (vertical axis wind turbine). HAWT's are typically characterized by the axis of rotation or longitudinal axis being oriented to be parallel or in line with the direction of the wind while VAWT's are typically characterized by the longitudinal axis of the turbine being oriented to be perpendicular to the direction of the wind.
VAWT's can further be classified into two main categories: 1) the Darrieus type windmill (more commonly known as egg-beater turbines) which consists of a central vertical tower having two or more curved rotor blades; and 2) the Savonius type windmill, which are drag type wind turbines having two or more scoops, such as those used in anemometers, radially extending from a central vertical tower. A giromill is a sub-type of the Darrieus windmill having straight planar rotor blades instead of curved blades, and the twisted Savonius windmill is a modified Savonius windmill having long helical scoops instead of smaller scoops.
GB Patent Application GB 2,057,584 to Burgdorf discloses a variation of the twisted Savonius windmill, having at least one double start helical turbine. Burgdorf teaches that it is important that the axis of rotation of the helical turbine is angled to the wind by 45° and that the pitch angle is of about 45°. Burgdorf teaches that the direction of the flow of the current relative to the central axis must be approximately equal to that of the pitch angle, as taught by Eielsen '957. However, Burgdorf specifically teaches that the angle is 45°
It appears that there is still room for higher efficiency utilization of rotor turbines and a need for a system capable of use in tidal, wind and uni-directional flow environments.